When assembling electronic devices, it is common to solder components to a printed circuit board (PCB) to attach components to the PCB. The soldering of components not only attaches the components to the PCB but may also be used to establish an electrical connection between the PCB and an electronic component. In this regard, both electrically coupled as well as non-electrically coupled components may be soldered to the PCB in order to maintain a position on the PCB.
Often components to be affixed to a PCB are positioned adjacent to the PCB with solder being positioned between the component and PCB. The assembly may then be heated such that the solder melts. When cooled, the solder may in turn solidify and attach the component to the PCB. This process of melting solder to affix a component to a PCB is commonly referred to as reflow.
During the assembly process of electronic devices, various tests may be conducted to determine whether the components that have been attached to the PCB are operative and properly attached. Examples of processes that may be conducted on a PCB to determine correct placement, attachment, and operation of components include function node testing and x-ray inspection. Based on the results of these tests, it may be necessary to remove components from the PCB due to a faulty attachment or other detected process defects. The removal of components may be necessary in order to replace a malfunctioning component, reattach a component, or access other components on the PCB. This process may be commonly referred to as rework.
For example, many PCBs include electro-magnetic (e.g., radio-frequency (RF)) shields that cover other components attached to the PCBs. Particularly in the field of electrical communication devices, RF shields may be employed to protect sensitive components from interference from RF energy. In this respect, many sensitive components may be located below an RF shield that is in turn attached to a PCB. Therefore, if one of the components contained under the RF shield needs to be removed or the RF shield itself needs replaced, the RF shield may need to be removed.
Existing methods for removal of RF shields often involve heating the RF shield with forced hot air to melt the solder attachment of the RF shield to the PCB. However, due to the difficulty in controlling a forced hot air process, directing the flow of hot air, the forced hot air heating of the RF shield may also create problems with other components and their solder joints. For example, the direction of the forced hot air may be difficult to control. As such, the forced hot air may be directed to portions of the PCB that are not to be reworked. Furthermore, the amount of heat transferred to the PCB is difficult to control in a forced hot air process. The temperature of the air existing the forced hot air source may be difficult to regulate and the amount of heat transferred may depend on many variables such as the temperature of the air existing the source, the distance of the source from the component, the flow rate of air existing the source, and other factors that may be variable and be difficult to control. The use of forced hot air may cause unintended reflow of adjacent components and may lead to solder joint defects in these adjacent components. These defects may occur to components adjacent to the RF shield that are not to be removed from the PCB. Examples include causing unintended reflow, delamination, plate lifting, wetting problems, dewetting problems, and other potential defects in components adjacent to the RF shield that has been heated with forced hot air. These defects may occur for components adjacent to the RF shield or components contained underneath the RF shield.
In addition to the potential for solder joint defects when using forced hot air to remove an RF shield, the process may be tedious and require a relatively long cycle time to remove the RF shield. The process generally involves an operator manipulating a forced hot air gun in order to heat the RF shield. The operator may be required to take great care to diminish the potential for solder joint defects in adjacent components. As such, the cycle time may be relatively long for each RF shield that needs to be removed. For instance, the cycle time for removing an RF shield with forced hot air heating may take between six to eight minutes and may require highly trained, certificated operators to operate the machine to reduce the potential for solder joint defects. Additionally, the equipment costs for the equipment necessary to perform forced hot air RF shield removal may be high.
Further still, once the RF shield has been heated by forced hot air heating, it is still necessary to remove the RF shield from the PCB. Existing methods for removal of an RF shield once heated by forced hot air heating include vacuum pick up and removing the RF shield manually by grasping (e.g., with tweezers). In this regard, the removal the RF shield once heated may be tedious and require high skill in order to prevent damage to the remainder the PCB when removing the RF shield with tweezers as adjacent components may also be heated such that they are susceptible to being damaged when manipulating portions of the PCB with tweezers.